EqualityComparable

The type must work with == operator and the result should have standard semantics.

Requirements

The type T satisfies EqualityComparable if.

Given.

a, b, and c, expressions of type T or const T

The following expressions must be valid and have their specified effects.

Expression	Return type	Requirements
`a == b`	implicitly convertible to `bool`	Establishes equivalence relation with the following properties: For all values of `a`, `a == a` yields `true`. If `a == b`, then `b == a` If `a == b` and `b == c`, then `a == c`

Notes

To satisfy this requirement, types that do not have built-in comparison operators have to provide a user-defined operator==.

For the types that are both EqualityComparable and LessThanComparable, the C++ standard library makes a distinction between equality, which is the value of the expression a == b and equivalence, which is the value of the expression !(a < b) && !(b < a).

Links:

http://en.cppreference.com/w/cpp/concept/EqualityComparable

doc_CPP

2016-10-11 09:58:33

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